Herpes simplex virus (HSV) attaches to cells by binding to cell surface heparan sulfate chains and then engages any one of several other cell surface molecules to trigger fusion between the virion envelope and a cell membrane, which leads to viral entry. The other cell surface receptors (entry receptors) include HVEM, a member of the TNF receptor family; nectin-1 and nectin-2, cell adhesion molecules of the Ig superfamily; and specific sites in heparan sulfate generated by certain 3-O-sulfotransferases. Virion gD is the ligand for all of these entry receptors. HSV-1 gD can bind to HVEM, nectin-1 and 3-O-sulfated heparan sulfate whereas HSV-2 gD can bind to HVEM, nectin-1 and nectin-2. Certain mutant forms of HSV-1 gD (Rid) have lost the ability to bind to HVEM and 3-O-sulfated heparan sulfate and acquired the ability to bind to nectin-2. The aims of the parent grant relate to the requirements for HSV entry into human cells and focus on structure/function studies of the entry receptors and characterization of their roles in HSV entry into specific human cell types. In this exploratory proposal, we intend to determine whether HSV-1 or HSV-1/Ridl gD can transduce or interrupt signals via any of the protein entry receptors and whether engagement of different entry receptors transduces different signals. Wild-type human fibroblasts expressing HVEM, nectin-1 and nectin-2 and mutant fibroblasts defective for nectin-1 expression will be used. These cells will be exposed to exogenous HSV-1 or HSV-1/Ridl gD or will be made to express each form of gD. RNAs will be isolated from the treated or mock-treated cells for comparisons of cell gene transcript levels by hybridization of labeled cRNAs to DNA oligonucleotide microarrays. Our hypothesis is that transduction or interruption of signals mediated by gD will result in changes in the levels of specific cell mRNAs and that the specific changes observed will depend on the particular receptor engaged by gD. If this proves to be the case, a long-term goal will be to determine whether signal transduction during viral entry influences post-entry events in viral infection in a receptor-dependent fashion. The studies described in this proposal are distinct from those supported by the parent grant but address questions that arise from findings made in the parent project.